Although she died in 1975, the majority of Elizabeth Taylor's 12 novels remain in print and are, thanks to Virago, regularly the recipients of efforts to stoke fresh interest in them; the most recent editions include prefaces by Hilary Mantel and Sarah Waters. Yet still she languishes unhappily in the literary margins, hovering somewhere below her contemporaries Rosamond Lehman and Antonia White in both the critical and the popularity stakes. Why? Partly, her trouble has long been her name which, as the title of this biography hints, is too easily confused with that of a certain violet-eyed movie star. Poor Elizabeth. Once, in a smart London store where she was buying a hat, an assistant said to her: "I think you must have been first with that name." And then, in an effort to lift Taylor's obvious gloom at the thought: "Well, I think you have more character. Although I shouldn't say it of one of my customers, the other one is very empty-headed."

But there are other factors. In their day, Taylor's books certainly sold, but they did so in spite of her attitude to publicity, which was mouse-like even by the standards of the 1950s. While she had literary friends, Elizabeth Bowen and Barbara Pym included, Taylor was not one for interviews, parties or the kind of bohemianism that ensures one will not be forgotten. When Ivy Compton-Burnett invited Taylor, one of her biggest admirers, to lunch, Taylor wrote to her friend Robert Liddell: "I am bidden again to lunch with Ivy. Command performance. I cannot go." (She did, though; one could not say no to Ivy, who once instructed Elizabeth that, should one get up in the night to go to the bathroom, it was imperative to put on "both your stockings and your knickers").

Taylor led a deliberately - you might say stubbornly - quiet life in rural Buckinghamshire, with her husband, a sweet manufacturer, and their two children, an existence that meant it was all too easy for her to be cast as a Home Counties writer of manners, one of those women who, as Stevie Smith put it, "sees life in terms of the daily domestic round, the children and the washing up and the clock ticking in the hall".

But this was unfair. Her best novels - At Mrs Lippincote's (1945), A View of the Harbour (1947), A Game of Hide and Seek (1951) - are, in spite of their prim titles, funny, savage and full of loneliness and suppressed emotion. For her characters, as for their author, propriety is a survival mechanism, a way of keeping the show on the road.

Nicola Beauman must, then, have come to Taylor's life hoping against hope there was more to it than met the eye, for all that she is a diehard fan of the novels. After all, Taylor had instructed that her letters be destroyed after her death; perhaps she had something to hide. As it turns out, she was right to hope. In her later years, her subject was certainly the very model of middle-class conformity, a rope of pearls always at her neck.

But her early life was strange and muddled to a degree that, reading about it, one's hunch about propriety hardens into belief: routine didn't only help her work, it helped her. There was something rebellious and disordered in Taylor, something that, though Beauman never states this explicitly, it is possible she rather feared.

She was born Betty Coles in Reading in 1912, the daughter of an insurance inspector, and attended the Abbey School, Jane Austen's alma mater. However, her poor results in maths ensured that she did not win a place at university and she worked variously as a governess and a librarian before marrying "up"; her husband, John, whom she met in local amateur dramatics, was the son of the mayor of High Wycombe and, unlike her, had grown up in a big house, with staff.

It was a surprising match, not least because Elizabeth, already determined to be a writer, had previously been attracted to a more free way of life. Eric Gill, the sculptor, lived with his menage nearby and, though Beauman is convinced that he did not seduce Taylor, it is certainly possible that she posed for him, nude. And perhaps this marriage was impulsive, the result both of grief - her mother had recently died - and girlish uncertainty, for soon afterwards she embarked on an affair with Ray Russell, an apprentice furniture designer and fellow communist (Taylor became a member in 1936, the year she married).

The affair was to last, on and off, for more than a decade, surviving even the war, when Russell was a PoW, and only ended properly in the late 1940s, when John, although himself unfaithful, told her that it must.

Beauman has, triumphantly, turned up the 500 letters Russell received from Taylor over her lifetime and these lie at the heart of her biography, providing insights both into Taylor's writing life - it took years of rejection before the publication of her first novel in 1945 - and into her personality, which was not quite so sweet as we were led to believe.

The letters she sent to Russell when he was a PoW make for astonishing reading. Taylor is so preoccupied with her own successes and failures as a novelist that she seems unable to write of anything else, least of all his plight. Reading them, it is impossible to escape the sense that she is using him, especially when she writes: "Nothing can be different in the future from how it was when you went away [before he went to fight, the couple had separated, though this was only temporary]. I can never give you anything but my friendship and the sort of love that is unacceptable to you." This writerly ego certainly puts her reputed shyness - her "little me" tendencies - into sharp relief.

Beauman has written an elegant biography for an elegant writer, with the result that even the boring bits of Taylor's life - when she is being a good wife and mother and dinner is always on the table - whip along charmingly. She is especially good on Taylor's influences: Virginia Woolf, Compton-Burnett and EM Forster.

But she also lets her love for Taylor get in the way, sticking up for her even when she is being needy and awful. Sometimes, her empathy is far too intrusive and syrupy for my liking. She is oddly delicate, too, writing that she could not bear to ask Russell, before his death, how it felt to lose Elizabeth (he seemed never to recover from her loss). Isn't this the job of the biographer?

Worst of all, she tells you how great a writer Taylor is far too often, using the word genius with too little care and acclaiming her, somewhat unconvincingly, as a great modernist. In this light, it's surprising to read that Taylor's children are "very angry and distressed" by her book, even though she waited until the death of the man who authorised it - John Taylor - to unveil it. They could not have hoped for a kinder, more generous account and it may well bring their mother new readers. I hope so.

The Other Elizabeth Taylor is published by Beauman's own company, Persephone Books, and is the first Persephone Life. A footnote here: Persephone, which publishes neglected novels by 20th-century (mostly women) writers, is 10 years old this year, and I for one wish it the happiest of birthdays. It is the most extraordinary, most lovely of publishers, as anyone who has ever bought, or been given, one of its beautiful dove grey books will testify. Its list, now 83 books strong, contains some duds (one of its most popular authors is Dorothy Whipple, who bores me to sobs), but mostly, it is a delight, including, as it does, work by Julia Strachey, Monica Dickens, Marghanita Laski, Richmal Crompton, Frances Hodgson Burnett, Noel Streatfield, Penelope Mortimer, and the great Molly Hughes. All to be read while eating violet creams, of course - or is that just a personal thing?

Elizabeth Jane Howard once said of Elizabeth Taylor: "How deeply I envy any reader coming to her for the first time." Since this is how I feel about certain of Beauman's girls, I would hereby like my deep gratitude to her to be noted.

Elizabeth Taylor: a life

1912 Born Betty Coles on 3 July in Reading, Berkshire. Attends the Abbey School in Reading and secretarial college. Works as a governess and librarian.

1936 Marries businessman John Taylor, with whom she has two children.

1945 After years of rejection, her first novel, At Mrs Lippincote's, is published.

1957 Angel, adapted for the big screen by François Ozon in 2007.

1971 Mrs Palfrey at the Claremont, made into a film starring Joan Plowright in 2005.